Noncontrolling Interest Represented by Preferred Operating Partnership Units - Additional Information (Details) $ / shares in Units, $ in Thousands											1 Months Ended	6 Months Ended			12 Months Ended
	Nov. 04, 2016 USD ($) shares	Jun. 15, 2016 USD ($)	May 21, 2016 USD ($) store shares	Oct. 03, 2014 USD ($) shares	Apr. 03, 2014 USD ($) store shares	Nov. 19, 2013 store	Sep. 26, 2013 USD ($) store shares	Aug. 29, 2013 store	Jun. 25, 2007 USD ($) shares	Jun. 15, 2007 store shares	Dec. 31, 2014 USD ($) store shares	Jun. 30, 2017 USD ($) shares store $ / shares	Jun. 30, 2016 USD ($)	May 31, 2014 USD ($) store shares	Dec. 31, 2016 USD ($) shares
Noncontrolling Interest [Line Items]
Note receivable from noncontrolling interest represented by Preferred Operating Partnership units												$ 120,230			$ 120,230
Cash Paid															42,149
Redemption of Operating Partnership units held by noncontrolling interests												$ 2,510	$ 0
Loan Assumed															$ 9,463
Number of stores acquired | store												5
Number of OP units issued for store acquisition (in units) | shares															272,400
Net Liabilities/(Assets) Assumed															$ (52)
Value of OP Units Issued															$ 6,810
Series B Redeemable Preferred Units [Member] | Series B Units [Member]
Noncontrolling Interest [Line Items]
Liquidation value (in dollars per share) | $ / shares												$ 25
Fixed liquidation value												$ 41,902
Annual rate of return (as a percent)												6.00%
Series B Redeemable Preferred Units [Member] | Series B Units [Member] | Georgia, 1 Property Acquired 4/3/2014 [Member]
Noncontrolling Interest [Line Items]
Preferred units issued as part of acquisition (in units) | shares					333,360
Preferred units issued as part of acquisition					$ 8,334
Series C Convertible Redeemable Preferred Units [Member] | California, Properties Acquired December 2013 [Member]
Noncontrolling Interest [Line Items]
Number of stores acquired | store						12
Ownership interests in five stores through joint ventures prior to the acquisition														35.00%
Number of stores in which ownership interest was held prior to acquisition of remaining properties | store														5
Ownership interest in one store through joint ventures prior to the acquisition														40.00%
Number of stores in which ownership interest was held prior to acquisition | store														1
Series C Convertible Redeemable Preferred Units [Member] | Series C Units [Member]
Noncontrolling Interest [Line Items]
Note receivable from noncontrolling interest represented by Preferred Operating Partnership units											$ 20,230
Note receivable interest rate											5.00%
Liquidation value (in dollars per share) | $ / shares												$ 42.1
Fixed liquidation value												$ 29,639
Quarterly distribution per preferred OP unit payable above quarterly distribution for common OP Unit (in dollars per share) | $ / shares												$ 0.18
Number of months immediately preceding the fifth anniversary of issuance for which distribution is payable												12 months
Period from date of issuance after which preferred OP units will become redeemable at the option of the holder												1 year
Preferred OP units conversion ratio | shares												0.9145
Note receivable maturity date											Dec. 15, 2024
Series D Redeemable Preferred Units [Member] | Series D Units [Member]
Noncontrolling Interest [Line Items]
Liquidation value (in dollars per share) | $ / shares												$ 25
Fixed liquidation value												$ 87,713
Series D Redeemable Preferred Units [Member] | D-1 Units[Member] | Minimum [Member]
Noncontrolling Interest [Line Items]
Annual rate of return (as a percent)												3.50%
Series D Redeemable Preferred Units [Member] | D-1 Units[Member] | Maximum [Member]
Noncontrolling Interest [Line Items]
Annual rate of return (as a percent)												5.00%
Operating Partnership [Member] | Illinois Property Acquired 5/21/2016 [Member]
Noncontrolling Interest [Line Items]
Number of stores acquired | store			4
Operating Partnership [Member] | Series A Participating Redeemable Preferred Units [Member]
Noncontrolling Interest [Line Items]
Number of stores acquired | store										10
Operating Partnership [Member] | Series A Participating Redeemable Preferred Units [Member] | Series A Units [Member]
Noncontrolling Interest [Line Items]
Preferred units issued as part of acquisition (in units) | shares										989,980
Fixed priority return on preferred OP units, amount		$ 115,000
Fixed priority return on preferred OP units, stated return rate		5.00%										2.25%
Fixed priority return on preferred OP units, liquidation value												$ 115,000
Operating Partnership [Member] | Series B Redeemable Preferred Units [Member] | Georgia, 1 Property Acquired 4/3/2014 [Member]
Noncontrolling Interest [Line Items]
Number of stores acquired | store					1
Cash portion of payment for acquisition					$ 15,158
Operating Partnership [Member] | Series B Redeemable Preferred Units [Member] | California, 20 Properties Acquired 2013-September [Member]
Noncontrolling Interest [Line Items]
Number of stores acquired | store							1	19
Cash portion of payment for acquisition							$ 100,876
Number of stores acquired as part of portfolio acquisition | store								20
Loan Assumed							$ 98,960
Number of common units issued as part of acquisition (in units) | shares							1,448,108
OP units issued as part of the acquisition							$ 62,341
Operating Partnership [Member] | Series B Redeemable Preferred Units [Member] | Series B Units [Member] | California, 20 Properties Acquired 2013-September [Member]
Noncontrolling Interest [Line Items]
Preferred units issued as part of acquisition (in units) | shares							1,342,727
Preferred units issued as part of acquisition							$ 33,568
Operating Partnership [Member] | Series C Convertible Redeemable Preferred Units [Member] | California, Properties Acquired December 2013 [Member]
Noncontrolling Interest [Line Items]
Cash portion of payment for acquisition														$ 45,722
Loan Assumed														$ 37,532
Number of stores acquired | store														6
Operating Partnership [Member] | Series C Convertible Redeemable Preferred Units [Member] | Series C Units [Member] | California, Properties Acquired December 2013 [Member]
Noncontrolling Interest [Line Items]
Preferred units issued as part of acquisition (in units) | shares														704,016
Preferred units issued as part of acquisition														$ 30,960
Operating Partnership [Member] | Series D Redeemable Preferred Units [Member] | Self Storage Facility in Florida [Member]
Noncontrolling Interest [Line Items]
Number of stores acquired | store											1
Cash portion of payment for acquisition											$ 5,621
Operating Partnership [Member] | Series D Redeemable Preferred Units [Member] | D-4 Preferred Units [Member] | Illinois Property Acquired 5/21/2016 [Member]
Noncontrolling Interest [Line Items]
Number of OP units issued for store acquisition (in units) | shares	486,244
Value of OP Units Issued	$ 12,156
Operating Partnership [Member] | Series D Redeemable Preferred Units [Member] | D-3 Units [Member] | Illinois Property Acquired 5/21/2016 [Member]
Noncontrolling Interest [Line Items]
Number of OP units issued for store acquisition (in units) | shares			2,201,467
Value of OP Units Issued			$ 55,037
Operating Partnership [Member] | Series D Redeemable Preferred Units [Member] | Series D Units [Member] | Self Storage Facility in Florida [Member]
Noncontrolling Interest [Line Items]
Preferred units issued as part of acquisition (in units) | shares											548,390
Preferred units issued as part of acquisition											$ 13,710
Operating Partnership Holders of A Units [Member] | Series A Participating Redeemable Preferred Units [Member]
Noncontrolling Interest [Line Items]
Note receivable from noncontrolling interest represented by Preferred Operating Partnership units									$ 100,000
Note receivable interest rate									4.85%			2.13%
Maximum number of preferred OP units converted prior to the maturity date of the loan (in units) | shares									114,500
A units redeemed | shares				114,500
Redemption of Operating Partnership units held by noncontrolling interests				$ 4,794
Common shares issued in Preferred Unit redemption (in shares) | shares				280,331
Additional units redeemed (in units) | shares				0